Bottles used for soft drinks and pressure applications require special base designs to efficiently contain the pressure. The best design to contain the pressure is a hemispherical one, but this will not allow the bottle to stand or be handled in filling lines, or be placed upright on a shelf.
To make a hemispherical base bottle stand, a base cup is attached to the bottle. Normally such base cups are injection molded of HDPE (High Density Polyethylene) and attached to polyester bottles using hot melt adhesives. The use of base cups implies tooling to manufacture, and inventory of base cups, a separate attaching operation, alignment problems, and base cups falling off during use. In addition if colored base cups are required to match the beverage or the graphics additional inventory is required. The cost is higher because of the base cup.
Recycling becomes an issue if the base cup material is different from the bottle material. For PET bottles, the base cups are HDPE causing recycling/and segregation problems.
Several novel inventions have been used to make one piece bottles to overcome the problem of base cups, and to provide pressure retention and the ability for the bottle to stand.
The most popular is the Petaloid base.
Other bases are the Conobase, (Krishnakumar et al U.S. Pat. No. 4,108,324), the Supa base (Pocock et al U.S. Pat. No. 4,525,401) and the champagne base, and Bartley, U.S. Pat. Nos. 5,004,109 and 5,066,081 for a skirt base. Bartley's invention has difficulty in axially stretching the skirt base and requires complex equipment.
All require additional material over a hemi-spherical base.